GB2121229A

GB2121229A - Methods and apparatus for recording and reproducing information signals

Info

Publication number: GB2121229A
Application number: GB08311005A
Authority: GB
Inventors: Takeo Eguchi
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1982-04-23
Filing date: 1983-04-22
Publication date: 1983-12-14
Also published as: US4636873A; JPS58185009A; GB2121229B; CA1210858A; GB8311005D0

Description

1 GB 2 121 229 A 1

SPECIFICATION

Methods and apparatus for recording and reproducing information signals This invention relates generally to apparatus for recording and reproducing information signals and, more particularly, is related to apparatus for recording and reproducing digital video signals in a plurality of record tracks extending obliquely on a magnetic tape. 5 Generally, a video tape recorder (VTR) includes at least one rotary magnetic head which records and/or reproduces video signals from a magnetic tape, with the magnetic head or heads being mounted on a rotary portion of a tape guide drum about which the tape is at least partially wrapped. However, various restrictions must be taken into consideration when constructing a VTR, for example, the number of magnetic heads, the tape wrapping angle'about the guide drum, and the like. 10 For example, where one rotary magnetic head is provided for recording and reproducing a video signal with respect to the magnetic tape, the timing of the video signal which is recorded and reproduced can not be freely varied because of the restrictions of a one head arrangement. Thus, with a VTR having a single rotary magnetic head, if synchronizing signals are not recorded on the magnetic 15 tape, synchronizing signals must be added to the video signal during reproduction in the interval during 15 which the rotary magnetic head does not contact the magnetic tape so as to compensate for the synchronizing signa Is that were not recorded. As a result, a constant restriction in the timing of the signal recorded by the rotary magnetic head exists in the interval during which the rotary magnetic head contacts the magnetic tape so that the wrapping angle of the magnetic tape on the tape guide drum can 20 not be freely varied. 20 On the other hand, with a VTR having two rotary magnetic heads positioned 1800 apart, that is, diametrically opposite to each other, the wrapping angle of the magnetic tape around the tape guide drum is 1800, thereby reducing the wrapping angle in comparison with that for a one head arrangement and providing the advantage that loading of the magnetic tape around the guide drum is easier. In such 25 case, a tape cassette containing the magnetic tape can be readily used with the VTR. It is to be 25 appreciated that, with the two head arrangement, the two rotary magnetic heads are selectively switched ON and OFF, or changed over, every 1800 so that the information signals recorded on and reproduced from the magnetic tape are continuous in time. Except for the fact that a margin is provided at both edges of the magnetic tape so as to avoid adverse affects when each rotary magnetic head first 30 contacts and terminates its contact with the magnetic tape, there are no direct advantages in increasing 30 the wrapping angle of the magnetic tape around the tape guide drum. Accordingly, the wrapping angle of the magnetic tape is selected to be approximately 180.

On the other hand, in a VTR equipped with two or more pairs of rotary magnetic heads, the timing of the information signal recorded ' on the magnetic tape can be freely varied so that it is unnecessary to specify a specific wrapping angle, for example, 3600 (3400), 1800 and 901 for two or more pairs of 35 rotary magnetic heads. In such case, however, an optimum wrapping angle should be chosen which optimally satisfies various conditions. Thus, the wrapping angle should be chosen taking into consideration the following conditions:

(1) The number of rotary magnetic heads and the number of channels with respect to the rotary 40 transformer must be as few as possible. 40 (2) The friction generated when the magnetic tape is wrapped around the tape guide drum must be sufficiently small and non-uniformity in contact of each rotary magnetic head with the magnetic tape, caused by, for example, sticking of the tape to the tape guide drum, non-uniformity or scattering in the air layer, and the like, must be minimized.

45 (3) The magnetic tape must be easily loaded around the tape guide drum with the magnetic tape 45 being conveniently contained in a tape cassette.

(4) A large amount of information in a narrow frequency band must be capable of being processed between the rotary magnetic heads and the rotary transformer.

In regard to condition (1), the fewest number of rotary magnetic heads is, of course, one. However, 50 as previously discussed in regard to the one head arrangement, the timing of the information signals 50 recorded on the magnetic tape is severely restricted, and the variety of signals that can be processed are also considerably restricted. In other words, a single rotary magnetic head system is not suitable for recording video information in digital form. Further, in accordance with present sampling standards for digital video signals, when the sampling frequencies are 13.5 MHz for the luminance signal and 6.75 55 MHz for the two color difference signals, 8 bits per sample are selected. In such case, the bit rate for the 55 digital video signal, including the blanking period, is 2 16 Mbits/sec, thereby requiring at least a 4-head and 2-channel system. In such system, two pairs of rotary magnetic heads are positioned apart with an angular spacing of 1800 and with each pair of rotary magnetic heads being formed of two adjacent rotary magnetic heads having magnetic gaps with different azimuth angles. It is to be appreciated that, 60 in such case, it is possible that the recording and playback rotary magnetic heads are separately 60 provided, or alternatively, that the rotary magnetic heads serve both for recording and playback.

In this regard, the 4-head and 2-channel system can be satisfactorily used for the high 216 Mbits/sec rate, while also providing a tape wrapping angle of 180', thereby enabling easy loading of the magnetic tape around the tape guide drum. Thus, except for the 4-head and 2-channel svstem. othpr 2 GB 2 121 229 A 2 systems do not meet the aforementioned conditions (1) and (4). The following Table compares the 4 head and 2-channel system with other systems as to the tape wrapping angle and Nyquist frequency.

TABLE

Number of Number of Tape Wrapping Nyquist Heads Channels Angle Frequency 1 1 3600 108 MHz 2 1 1800 108 MHz 2 2 3601 54 MHz 3 1 1200 108 MHz 3 3 3601 36 MHz 4 1 900 108 MHz 4 2 1800 54 MHz 4 4 3601 27 MHz f However, as shown in the above Table, the 4-head and 2-channel system requires a significantly 5 high Nyquist or minimum sampling frequency of 54 MHz. Consideing the frequency characteristics of 5 the rotary magnetic heads, the rotary transformer and the recording and reproducing amplifiers, it is thereby quite difficult to put the 4-head and 2-channel system into practice. In view of these problems, it is desirable to provide a VTR operable with a lower Nyquist frequency, yet capable of providing a high signal-to-noise (S/N) ratio with a sufficiently wide frequency range, while also not increasing the 10 diameter of the tape guide drum. 10 Accordingly, it is an object of this invention to provide a method and apparatus for recording and/or reproducing information signals that avoids the above-described difficulties encountered with the aforementioned arrangements.

More particularly, it is an object of this invention to provide a method and apparatus for recording 15 and/or reproducing digital video signals with a low Nyquist frequency. 15 It is another object of this invention to provide a method and apparatus for recording and/or reproducing information signals with a high S/N ratio without increasing the size of the tape guide drum.

It is still another object of the invention to provide a method and apparatus for recording and/or reproducing information signals with a high S/N ratio and with a sufficiently wide frequency range.

20 In accordance with an aspect of this invention, apparatus for recording and reproducing original 20 information signals in a plurality of tracks on a record medium, includes a recording section having time base expansion means for expanding the time base of the information signals to produce time base expanded information signals, and a plurality of magnetic heads for recording the time base expanded information signals on the record medium; and a reproducing section having a plurality of magnetic 25 heads for reproducing the time base expanded information signals from the record medium, and time 25 base compression means for time base compressing the time base of the time base expanded information signals to produce the original information signals.

The above, and other, objects, features and advantages of the present invention will become apparent from the following detailed description thereof which is to be read in connection with the

30 accompanying drawings. 30 Fig. 1 is a schematic diagram of a rotary magnetic head assembly in accordance with one embodiment of the present invention; Fig. 2 is a schematic diagram showing the magnetic gaps of some of the rotary magnetic heads of Fig. 1; 35 Fig. 3 is a schematic diagram showing the magnetic gaps of the remaining rotary magnetic heads 35 of Fig. 1; Fig. 4 is a schematic diagram showing the arrangement of record tracks formed bv each r)air of recording rotary magnetic heads according to the present invention; Fig. 5 is a block diagram of a recording section of a VTR according to one embodiment of the 40 present invention; 40 Fig. 6 is a timing chart used for explaining the operation of the recording section of Fig. 5; 3 GB 2 121 229 A 3 Fig. 7 is a block diagram of a reproducing section of a VTR according to one embodiment of the present invention; and Fig. 8 is a timing chart used for explaining the operation of the reproducing section of Fig. 7.

Referring to the drawings in detail, and initially to Fig. 1 -thereof, a rotary magnetic head assembly 5 for recording and reproducing information signals, preferably digital video signals, according to this 5.

invention includes a tape guide drum DR which may be comprised of an upper rotary drum and a lower fixed or stationary drum, or alternatively, upper and lower fixed or stationary drums and a middle rotary drum. A magnetic tape TP is wrapped about the outer periphery of guide drum DR so as to subtend an angle of 0. Magnetic tape TP is advanced at a constant speed about tape guide drum DR by a tape drive 10 system (not shown) comprised of a capstan and pinch roller and is guided about tape guide drum DR by 10 tape guide pins or rollers TG1 and TG2 which determine the tape wrapping angle 0.

Secured to the rotary guide drum of tape guide drum DR are recording rotary magnetic heads HRI-HR4 and reproducing rotary magnetic heads H,,-H,,. More particularly, the recording rotary 15 magnetic heads are arranged in pairs HR, HR2 and HR3, HR4, each pair being positioned diametrically opposite the other pair, that is, 1800 apart therefrom. In like manner, the reproducing rotary magnetic 15 heads are formed in two pairs H,1, HP2 and HP3, Hp4, with the two pairs of reproducing rotary magnetic heads being positioned diametrically opposite to each other, that is, 1801 apart, and with each pair of reproducing rotary magnetic heads being separated from each adjacent pair of recording rotary 20 magnetic heads by an angular spacing of 901.

The recording and reproducing rotary magnetic heads are constructed such that recording rotary 20 magnetic heads H,, and H13 and reproducing rotary magnetic heads H,1 and H,, have a magnetic gap g, with the same azimuth angle, as shown in Fig. 2, while the remaining recording rotary magnetic heads H.2 and H.4 and the remaining reproducing rotary magnetic heads H,, and H, , have a magnetic gap 92 with a second azimuth angle which is identical in value but opposite to the first azimuth angle, as shown 25 in Fig. 3. It is therefore to be appreciated that the rotary magnetic heads of each pair have magnetic 25 gaps g, and 92 with opposite azimuth angles. In this manner, each pair of rotary magnetic heads H,,, HR2 and HR3, HR4 are adapted to record information signals in adjacent parallel record tracks T, and TV respectively, extending obliquely on magnetic tape TP, with opposite azimuth angles, as shown in Fig. 4.

During reproduction, the information signals in tracks T, and T2 are reproduced by, for example, pairs of 30 reproducing rotary magnetic heads Hpl, HP2 and HP3r Hp, respectively. 30 As previously discussed, a 4-head and 2-channel arrangement requires a high Nyquist frequency.

It is therefore desirable to reduce the Nyquist frequency, and thereby narrow the allowable frequency band of the signals to be recorded, to reduce the cost and complexity of the magnetic heads, rotary transformer and processing circuitry. It is to be appreciated that, with the above arrangement, the 35 wrapping angle 0 necessary for real time recording and reproduction of information signals is 1801, as 35 shown in the above Table. However, the frequency characteristic, that is, the allowable frequency band of the signals, through the rotary magnetic heads, the rotary transformer and the like is narrowed in reverse proportion to the wrapping angle 0. Thus, in accordance with the present invention, the tape wrapping angle 0 is increased without increasing the size of the tape guide drum, thereby reducing the 40 required Nyquist frequency and narrowing the frequency band of the signals that are recorded. 40 However, it is to be appreciated that, in accordance with the present invention, the frequency band of the signals are sufficiently wide for good recording and reproduction.

However, there are certain limitations as to how much the wrapping angle 0 can be increased.

From the point of view of friction of magnetic tape TP against tape guide drum DR and the loading 4 5 mechanism for loading magnetic tape TP around tape guide drum DR when magnetic tape TP is 45 contained within a tape cassette, it becomes impractical to select the tape wrapping angle 0 equal to 3600. Further, if tape guide drum DR is comprised of upper and lower stationary drums and a middle rotary drum, the support structure for the upper and lower stationary drums occupies an angular spacing of at least 901, as shown at points A and B in Fig. 1. Taking the above limitations into 50 consideration, the tape wrapping angle 0 of magnetic tape TP around tape guide drum DR is made less 50 than 2700. Practically speaking, however, further taking into consideration the positioning of tape guide pins TG1 and TG2, a maximum wrapping angle 0 is equal to approximately 2400. In such case, the Nyquist frequency fN that is required is calculated as follows:

180 (1) fN = 54 x - = 40.5 MHz 240 55 It is to be appreciated that, with the wrapping angle increased to 2401, the Nyquist frequency is 55 25% less than that for the case where the wrapping angle is selected as 1801. Preferably, the tape wrapping angle 0 is selected to be greater than 1801 and less than 2401. For example, when the tape wrapping angle is selected as 2201, the Nyquist frequency fN is 44.2 MHz. In such case, the diameter of tape guide drum DR may be, for example, 110 mm. It is to be noted that, if tape guide drum DR is 60 comprised of an upper rotary guide drum and a lower stationary drum, the tape wrapping angle can 60 more freely be selected in comparison to the case where tape guide drum DR is comprised of upper and lower stationary drums and a middle rotary drum.

GB 2 121 229 A It is to be appreciated that, since the tape wrapping angle 0 is increased from the nominal real time tape wrapping angle of 1800, while maintaining the size of the tape guide drum, the rotary magnetic heads are in contact with magnetic tape for a longer length thereof. Thus, the information signals must be time base expanded. In this regard, and referred to Figs. 5 and 6, the information signals 5 are time base expanded prior to recording the same in the record tracks, in accordance with the present 5 invention. As shown in Fig. 5, an analog information signal, such as an analog color video signal, is supplied through an input terminal 2 to a recording digital processing circuit 4 which converts the analog video signal to a digital video signal and channel encodes the digital video signal so as to separate the digital video signal into two channels. The digital video signal in one channel is supplied to 10 time base expansion circuits 6A and 6C, while the digital video signal in the other channel is supplied to 10 time base expansion circuits 613 and 61), the time base expansion circuits functioning to expand the time base of the-digital video signals supplied thereto. The time base expanded signals from time base expansion circuits 6A-6D are supplied through recording amplifiers 8A-8D to recording rotary magnetic heads HIR1-HR4, respectively, which record the digitized video signals in successive, parallel 15 record tracks extending obliquely on magnetic tape TP.

In operation, for every field or one-half field interval, the analog video signal from input terminal 2 is divided by recording digital processing circuit 4 into analog video signals SP S2, S3, S41,.. and converted into digital form. The digitized signals SP S2, S3, S4. are then each further divided into two channel digital video signals and supplied to the two channels, respectively. For example, digital video 20 signal S1 is separated into digital video signals S, and S12, which are supplied to time base expansion circuits 6A and 6B, respectively, where the signals have their time base expanded, as shown in Fig. 6.

The time base expanded signals S,, and SU from time base expansion circuits 6A and 6B, respectively, are supplied through recording amplifiers 8A and 813 to recording rotary magnetic heads H R, and HR2 which record the expanded signals S,, and SU in adjacent parallel tracks extending obliquely on 25 magnetic tape TP, for example, as shown in Fig. 4. The subsequent digital video signal S2 is then 25 separated into two channel digital video signals S21 and S22 which are supplied to time base expansion circuits 6C and 6D, respectively, which expand the time base of such signals, as shown in Fig. 6. Time base expanded signals S21 and S22 are then supplied through recording amplifiers 8C and 8D to recording rotary magnetic heads HR3 and I-IF14, respectively, which record signals S2, and S22 in the next 30 pair ot record tracks on magnetic tape TP. In like manner, signal S3 is separated into channel signals S31 30 and S32 and supplied through time base expansion circuits 6A and 613 and recording amplifiers 8A and 813 to magnetic heads HR, and HR2, respectively, which record the expanded signals S31 and S.2 in the next pair of adjacent tracks. In like manner, signal S4'S separated into channel signals S41 and S42 and supplied through time base expansion circuits 6C and 6D and recording amplifiers 8C and 81) to 35 magnetic heads HR3 and HR4, respectively, which record the time base expanded signals S4, and S42 in 35 the next pair of adjacent record tracks on magnetic tape TP. It is to be appreciated, as previously discussed, that adjacent recording rotary magnetic heads HR, and H.2 of one pair have magnetic gaps with opposite azimuth angles so that the channel signals, for example, channel signals S, l and S12, supplied thereto are recorded in adjacent tracks with different azimuth angles, as shown in Fig. 4. In like 40 manner, recording rotary magnetic heads H.3 and HR4 of the other pair of magnetic heads also have magnetic gaps with opposite azimuth angles. Thus, in accordance with the present invention, because the tape wrapping angle 0 is increased, the recording rotary magnetic heads are in contact with magnetic tape TP for a longer period of time and it therefore becomes necessary to expand the time base of the video signals recorded thereby.

45 Referring now to Fig. 7, a reproducing section of a VTR according to the present invention includes 45 reproducing rotary magnetic heads H,,-HP4 which are arranged in pairs, as previously discussed in regard to Fig. 1. In this manner, the expanded video signals S,., and S12 are reproduced by magnetic heads Hp, and HP2, respectively, and supplied through reproducing amplifiers 1 OA and 1 OB to time base compression circuits 12A and 1213, respectively. The latter time base compression circuits 12A and 12B time base compress the expanded video signals S,, and S12, respectively, to return the expanded signals 50 to their original time base, as shown in Fig. 8, and supplies the same through mixing circuits 14 and 16, respectively, to a reproducing digital processing circuit 18 which combines the signals to form digital video signal Si. The latter circuit then returns digitized video signal S, to analog form and supplies the same to an output terminal 20. Subsequent thereto, when rotary magnetic heads HP3 and HP4 trace the 55 next pair of adjacent record tracks on magnetic tape TP, expanded video signals S21 and S22 are supplied 55 through reproducing amplifiers 10C and 1013to time base compression circuits 12C and 12D, respectively, which return the expanded signals to their original time base, as shown in Fig. 8. The output signals from time base compression circuits 12C and 12D are then supplied through mixing circuits 14 and 16, respectively, to reproducing digital processing circuit 18 which combines the signals 60 to form digital video signal S21 converts the same into analog form and supplies analog video signal S2 60 to output terminal 20. In like manner, reproducing magnetic heads Hp, and HP2 reproduce expanded video signals S,, and S.2 during the trace of the next two adjacent tracks, and reproducing magnetic heads HP3 and HP4 reproduce expanded video signals S41 and S42 during the trace of the next two adjacent tracks. In this manner, the original continuous analog video signal is supplied to output terminal 20.

5 GB 2 121 229 A 5 It is to be appreciated that various modifications within the scope of the present invention can be made to the above-described embodiment. For example, although the present invention has been preferably described with respect to digital video signals, the present invention may be utilized with audio signals or a combination of video and audio signals, in analog or digital form. In addition, although 5 the recording and reproducing rotary magnetic heads have been provided separately, the same rotary 5 magnetic heads can be used in common for both recording and reproducing. In addition, although only two pairs of rotary magnetic heads have been shown for recording and reproducing, two or more pairs of rotary magnetic heads can be used for recording and reproducing with the present invention. For example, if four pairs of rotary magnetic heads are used each for recording and reproducing, although 10 the nominal real time wrapping angle 0 is selected as 901, with the present invention the wrapping 10 angle 0 can be increased to an angle greater than 900, for example, approximately 1200. In this manner, without increasing the size of the tape guide drum, a high signalto-nolse (S/N) ratio, with a sufficiently wide frequency range is provided.

Having described a specific preferred embodiment of the invention with reference to the 15 accompanying drawings, it is to be understood that the present invention is not limited to that precise 15 embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

Claims

1. Apparatus for recording information signals in a plurality of tracks on a record medium, 20 comprising: 20 time base expansion means for expanding the time base of said information signals to produce time base expanded information signals; and a plurality of transducer means for recording said time base expanded information signals in said plurality of tracks on said record medium.

25

2. Apparatus according to claim 1, in which said plurality of transducer means are arranged in 25 pairs, one transducer means of each pair having a magnetic gap with a first azimuth angle and the other transducer means of the respective pair having a magnetic gap with a second, different azimuth angle.

3. Apparatus according to claim 2, in which said first and second azimuth angles are equal and opposite.

30

4. Apparatus according to claim 2, in which said transducer means of the same pair are positioned 30 adjacent to each other.

5. Apparatus according to claim 2, further including N pairs of transducer means, where N 2, said N pairs of transducer means being equally spaced from each other by an angle 3601/K

6. Apparatus according to claim 2, further including means for separating said time base expanded 35 information signals into two channel signals and supplying said two channel signals to each pair of 35 transducer means, respectively.

7. Apparatus according to claim 1, in which said information signals are analog signals; and further including means for converting said analog signals to digital form prior to recording by said plurality of transducer means.

40

8. Apparatus according to claim 1 or 2, further comprising guide drum means for rotation with 40 said plurality of transducer means, and in which said record medium is a magnetic tape which is wrapped at least partially around said guide drum means for an angle greater than a nominal angle for real time recording of said information signals.

9. Apparatus according to claim 8, in which two pairs of rotary magnetic heads are provided, with 45 each pair being positioned diametrically opposite the other pair, and in which said magnetic tape is 45 wrapped around said guide drum means for an angle 0, where 0 > 180'.

10. Apparatus according to claim 9, in which 1800 < 0:5 2400.

11. A method of recording information signals in a plurality of tracks on a record medium, comprising the steps of:

50 expanding the time base of said information signals to produce time base expanded information 50 signals; and recording said time base expanded information signals in said plurality of tracks on said record medium with a plurality of transducer means.

12. A method according to claim 11, in which said record medium is a magnetic tape, and further 55 comprising the step of wrapping said magnetic tape at least partially around guide drum means for an 55 angle greater than a nominal angle for real time recording of said information signals.

13. A method according to claim 12, in which two pairs of rotary magnetic heads are provided with each pair being positioned diametrically opposite the other pair, and in which said magnetic tape is wrapped around said guide drum means for an angle 0, where 0 > 180'.

60

14. A method according to claim 13, in which 1801' < 8:! 240'. 60

15. Apparatus for reproducing original information signals that have been time base expanded and recorded in a plurality of tracks on a record medium, comprising:

a plurality of transducer means for reproducing said time base expanded information signals from said plurality of tracks on said record medium; and GB 2 121 229 A 6 time base compression means for time base compressing said time base expanded information signals to produce said original information signals.

16. Apparatus accor(ling to claim 15, in which said plurality of transducer means are arranged in pairs, one transducer means of each pair having a magnetic gap with a first azimuth angle and the other 5 transducer means of the respective pair having a magnetic gap with a second, different azimuth angle. 5

17. Apparatus according to claim 16, in which said first and second azimuth angles are equal and opposite.

18. Apparatus according to claim 16, in which said transducer means of the same pair are positioned adjacent to each other.

10

19. Apparatus according to claim 16, further including N pairs of transducer means, where N > 2, 10 said N pairs of

20. Apparatus according to claim 16, in which said time base expanded signals are separated into two channel signals prior to recording in said plurality of tracks; and further including means for combining said two channel signals to produce said time base expanded signals.

15

2 1. Apparatus according to claim 15, in which said time base expanded signals are digital signals; 15 and further including means for converting said digital signals to analog form.

22. Apparatus according to claim 15, further comprising guide drum means for rotation with said plurality of transducer means, and in which said record medium is a magnetic tape which is wrapped at least partially around said guide drum means for an angle greater than a nominal angle for real time reproduction of said information signals.

23. Apparatus according to claim 22, in which two pairs of rotary magnet. c heads are provided with each pair being positioned diametrically opposite the other pair, and in which said magnetic tape is wrapped around said guide drum means for an angle 0, where 0 > 180'.

24. Apparatus according to claim 23, in which 1801 < 0: 240'.

25 25. A method of reproducing original information signals that have been time base expanded and 25 recorded in a plurality of tracks on a record medium, comprising the steps of:

reproducing said time base expanded information signals from said plurality of tracks on said record medium with a plurality of transducer means; and time base compressing said time base expanded information signals to produce said original information signals.

26. A method according to claim 25, in which said record medium is a magnetic tape, and further comprising the step of wrapping said magnetic tape at least partially around guide drum means for an angle greater than a nominal angle for real time reproduction of said information signals.

27. A method according to claim 26, in which two pairs of rotary magnetic heads are provided, with each pair being positioned diametrically opposite the other pair, and in which said magnetic tape is 35 wrapped around said guide drum means for an angle 0 where 0 > 180'.

28. A method according to claim 27, in which 1800 < 0 < 2401.

29. Apparatus for recording and reproducing original information signals in a plurality of tracks on a record medium, comprising:

40 a recording section having time base expansion means for expanding the time base of the 40 information signals to produce time base expanded information signals, and a plurality of transducer means for recording the expanded information signals in the plurality of tracks on the record medium; and 20 # a reproducing section having a plurality of transducer means for reproducing the time base expanded information signals from the record medium, and time base compression means for time base 45 compressing the time base of the reproduced time base expanded information signals to produce the original information signals.

30. A method of recording and reproducing original information signals in a plurality of tracks on a record medium, comprising the recording steps of:

50 expanding the time base of the information signals to produce time base expanded information 50 signals; and recording the time base expanded information signals in the plurality of tracks on the record medium with a plurality of recording transducer means; and comprising the reproducing steps of:

55 reproducing the time base expanded information signals from the record medium with a plurality 55 of reproducing transducer means, and time base compressing the time base of the time base expanded information signals to produce the original information signals.

3 1. Apparatus for recording information signals constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

32. Apparatus for reproducing information signals constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

33. A method of recording information signals substantially as hereinbefore described with reference to and as illustrated in the accompanvincl drawinas.

I GB 2 121 229 A 7 34, A method of reproducing information signals substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office, Southampton Buildings, London, WC2A IAY, from which copies may be obtained.

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